Local ecological impacts from biodiesel production units are most likely to be severe in areas of the world with lax environmental policies or enforcement. This is a par­ticularly acute problem for biodiesel production because of the potential to generate large volumes of aqueous wastes with high biological demands. Glycerol is a major waste product unless it is exploited as an income-generating stream, but this is not always economically feasible.58 Biodiesel wastes containing glycerol can be utilized by a Klebsiella pneumoniae strain to produce hydrogen by fermentation as a source of locally generated combustible gas for local heating or on-site use for biomass drying.72 A second biohydrogen system was based on an Enterobacter isolated from methanogenic sludge; glycerol-containing biodiesel wastes were diluted with a syn­thetic medium to increase the rate of glycerol consumption and the addition of nitro­gen sources (yeast extract and tryptone) enhanced the rates of both hydrogen and ethanol formation.73 In general, however, wastewater streams from biodiesel plants are not considered suitable for microbial remediation because of the high-pH, hex­ane-extractable oil, low nitrogen concentrations, and the presence of growth inhibi­tors; an oil-degrading Rhodotorula mucilaginosa yeast was found to degrade oil in wastewaters diluted with water to reduce growth inhibition and the content of solid materials, and this was developed into a small-scale treatment method.74

Especially in Europe, however, possible environmental damage is more often viewed as an international issue. This can be traced back to the initial period of biodiesel production in the 1980s, when it became evident that land resources inside the European Union were highly likely to limit biodiesel manufacturing capacity with European feedstocks: by 1992, oilseed rape cultivation in the United King­dom (barely known in the 1970s) was estimated to cover 400,000 hectares of land, enough crop to satisfy no more than a 5% substitution of conventional diesel sales.4 Twenty-five years later, the United Kingdom was devoting 570,000 hectares to grow­ing oilseed rape but 40% of this was for food use (cooking oil, margarine, etc.); even if all this land and whatever land is “set aside” under Common Agricultural Policy, policies could still only support a 5% (or less) substitution of fossil diesel.75 Even if all the U. S. soybean crop were to be devoted to biodiesel production, only 6% of U. S. diesel demand could be met.60 To meet U. S. and EU targets, therefore, importing biodiesel feedstocks is probably unavoidable, and this is (equally probably) depen­dent on supplies from Africa and Asia, with energy crops grown on recently cleared, deforested land; net importers can limit their imports from countries operating under plans such as the Round Table on Sustainable Palm Oil, an initiative to legitimize the trade in sustainably produced feedstock, but have often proved reluctant to ban imports of unsustainable biofuel sources for fear of breaching World Trade rules.76

To increase the pressure on available arable land further, biodiesel from mono­culture crops such as soybean and canola support much poorer energy production rates than does corn-based ethanol.77 The International Energy Agency has predicted that the land requirements for biofuels production will increase from a global figure of 1% in 2004 to 2.5% by 2030 — or, under alterative scenarios, to 3.8% or even 4.2% (58.5 million hectares).2 The search for high-yielding energy crops suitable

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* Brazilian sugarcane-derived ethanol may, depending on the sugarcane price, be cheaper to produce than conventional gasoline and represent a negative abatement cost (figure 6.7).

rural employment, and forms part of the government’s policies to eliminate poverty; targets under “Probiodiesel” include 2% of all transport diesel to be biodiesel by 2008 (when all fuel distributors will be required to market biodiesel) and 5% by 2013.80 As a chemical technology, biodiesel production is easily integrated with the existing infrastructure of heavy chemical industry, sharing sites and power costs: a BASF maleic anhydride plant at Feluy (Belgium) shares waste heat with a biodiesel production unit operated by Neochim.81 Industrial plants that used to produce glyc­erol are now closing down to be replaced by others that use glycerol as a raw material, owing to the large surplus of glycerol formed as a coproduct during the production of biodiesel; in parallel, research efforts to find new applications of glycerol as a low — cost feedstock for functional derivatives have led to the introduction of a number of selective processes for converting glycerol into commercially valued products.82

Although the public face of soybean oil-derived biodiesel in Brazil and elsewhere remains that of sustainable symbiotic nitrogen fixation with the bacterium Bradyrhi- zobium japonicum and soybean cultivars selected to grow in the arid savannah in the hinterland state of Mato Grosso, environmentalist concerns about “deforestation diesel” remain acute: Brazil already exports 20 million tonnes of soybean annually and plans to increase this to 32 million tonnes by 2015.83 To what extent soybean — plantation cultivation encroaches from savannah to adjacent rain forest will largely determine how “sustainable” this major source of biodiesel feedstock will prove.